The capacity to direct migration of blood-borne cells to a predetermined location (“homing”) has profound implications for a variety of physiologic and pathologic processes. Recruitment of circulating cells to a specific anatomic site is initiated by discrete adhesive interactions between cells in flow and vascular endothelium at the target tissue(s).
Selectin-mediated interactions are critical not only for the rapid and efficient recruitment of leukocytes at a site of injury, but for steady state, tissue-specific homing as illustrated in: (1) lymphocyte homing to peripheral lymph nodes, (2) cutaneous tropism of human skin-homing T-cells and (3) hematopoietic progenitor cell (HPC) entry into bone marrow.